Business and consumers use a wide array of wireless devices, including cell phones, wireless local area network cards, global positioning system devices, electronic organizers equipped with wireless modems, and the like. The increased demand for wireless communication devices has created a corresponding demand for technical improvements to such devices. Generally speaking, more and more of the components of conventional radio receivers and transmitters are being fabricated in a single integrated circuit package. In order to simplify single chip designs and to make each design suitable for as many applications as possible, much emphasis has been placed on developing on-chip voltage regulators.
Many applications use on-chip voltage regulators to provide accurate regulated voltages for the core circuit on the chip. In these applications, the load is generally a large capacitive load. Thus, the reference voltages required for these applications have to be extremely accurate in order for the voltage regulators to generate accurate regulated output voltages.
Conventional voltage regulators include an error amplifier and two voltage sources. One voltage source provides a reference voltage and the other provides a bias voltage. The error amplifier generates an output voltage based on the reference and bias voltages provided by the voltage sources. However, disadvantages associated with conventional voltage regulators include relatively high, unavoidable output voltage variations due to process, temperature and voltage variations. These varying conditions may result in an output voltage swing of up to 200 mV, which is too high for some applications.
Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.